To break up the soil, moldboard and rotary disk plows are already known and now used. Moldboard plows are widely used in countries with highly developed agriculture. In our country, they have not been used extensively, disk plows being more popular and now used by the majority of farmers. On both types of plows are devices to make the tractor go back and forth and the plow to turn the earth in the same direction.
Disk plows are made up of a series of rotary concave disks mounted individually and supported by a frame; their penetrating effect into the earth occurs mainly from weight although it is also affected by the vertical and horizontal position of the disk.
The width of the cut made by the disk is affected by the size of the disk, since if it is spaced too widely it leaves an area of earth without turning it over by its parabolic cut.
Since the disks are rotary, they allow a bidirectional operation solely by reversing the direction the disk faces.
To compensate for the lateral force of the disk and to control the depth, these plows require a rear wheel.
Of course, the disadvantage of fixed disk plows is that the farmer must plow the field by making turns from the edges to the center of the field, while reversible plows allow the earth to be worked parallel back and forth, creating equal furrows without leaving free spaces.
Now, moldboard plows for their part can have a single set of moldboards that can turn the earth only in one direction and it is necessary to work in strips or series of parallel furrows, leaving the surface uneven.
There are designs for moldboards of different speeds, widths of cut and types of soil. The bodies of the moldboards occasionally require a disconnecting device for uneven ground with stumps, rocks or hard strips. Each moldboard requires a wear plate or heel to compensate for the lateral force and to control the depth.
The moldboards of present plows are fastened to supports and the latter in turn are fastened to the main frame. Their effect of penetration into the soil is achieved by suction when pulled by the tractor, not having limitations of cutting width and they do not leave the earth without turning it over, since their cut is straight.
There are also plows with two sets of left and right moldboards which permit a reversible action, since the tractor can reverse direction and, despite this, the earth can be turned on the same side, which makes it possible to start the work at one end of the land and end at the other, resulting in a better leveled surface.
However, the disadvantage of the reversible plows with two sets of moldboards is that the stability of the tractor is limited, due to the additional weight of the extra set of moldboards and in many cases the tractive power of the tractor is wasted for the reason described above.